Sleep in right hemispherectomized patients: evidence of electrophysiological compensation

Objectives: The goal of this study is to provide a better understanding of the role of the cortex in sleepʹs macro- and microstructure modulation. Methods: Sleep architecture and phasic events were investigated in 4 patients having undergone right functional or anatomical hemispherectomy and 8 control subjects. Between-groups differences were assessed using the Wilcoxon–Mann–Whitney test. Results: Findings provide evidence for overall similarity between patientsʹ and control subjectsʹ left hemispheric sleep architecture. In addition, results clearly indicate that it is possible to detect electrical activity over the operated side of a hemispherectomized patientʹs brain, even when resection of the hemi-cortex has been complete. Finally, findings provide evidence for similar left and right hemispheric relative spectral activities and for an increase in fast activity bands over the intact hemisphere in anatomical hemispherectomized patients. Conclusions: This study provides evidence that right hemispherectomy does not produce significant sleep architecture alterations as recorded over the intact hemisphere. In addition, residual activity detected over the operated side in anatomical hemispherectomized patients is interpreted as resulting from volume conduction originating from generators located in the intact hemisphere. Finally, there is strong evidence for electrophysiological compensation in the intact hemisphere following complete resection of the contralateral hemi-cortex.